Small signal modulation characteristics of quantum dot lasers and the effect of annealing and doping

Abstract

The demand for bandwidth capacity is increasing exponentially due to the spread of high-speed internet services. A significant increase in capacity is achieved in fibre optical access networks. Semiconductor lasers operating at wavelengths around 1.3 μm, where the standard single mode fibre has minimum dispersion, are key components in such networks. Thus, they have attracted much research interest in recent years.The discovery of self-organized epitaxial quantum dots (QDs) resulted in multiple breakthroughs in the field of the physics of zero-dimensional (0-D) heterostructures and allowed the advancement of optoelectronic devices. The most remarkable advancement involved lasers. The most advanced results obtained for lasers are based on the InGaAs/GaAs QDs by the Stranski-Krastanow growth. InAs is currently the most optimized candidate material for constructing low-cost and high-performance QD lasers on GaAs substrates because of its low threshold current density and its temperature insensitivity compared to lasers made from the conventional InGaAs/InP material system. Superior static performances have been demonstrated for 1.3 μm InAs/GaAs QD lasers. However, InAs/GaAs QD lasers have not fulfilled the initial expectation of demonstrating superior dynamic characteristics over Quantum Well (QW) lasers.The aim of this research study is to characterize the performances of InAs/InGaAs QD lasers and to suggest a method to improve these performances through p-doping and post-growth rapid thermal annealing. A systematic study has been performed on undoped and p-doped ten-layer InAs/InGaAs QD lasers to investigate the characteristic parameters related to lasing behaviour. The high-speed performance of these lasers will be targeted.